Double-beam high resolution Fourier spectrometer for the far infrared.

The construction and the performance of a double-beam Michelson-type Fourier spectrometer are described. The instrument covers a wavenumber range from 10 cm(-1) to 450 cm(-1) with a maximum resolution of 0.025 cm(-1) and an accuracy of frequency within +/-0.001 cm(-1). The optical path difference is measured by means of an He-Ne gas laser. To illustrate the general performance of the instrument, the pure rotational spectra of H(2)O and CO have been recorded.